Tropical spiders can hide for 30 minutes underwater

A tropical spider uses air membranes to hide under water and hide from predators for half an hour, surprising scientists.

The air membrane makes the spider look like it's covered in silver.

Lindsey Swierk, assistant professor of biology at Binghamton University in New York, observes a large species of tropical spider (Trechalea extensa) that flees from humans and hides in the water. Previously, researchers did not know this spider was able to use the water surface to escape for so long. "For many animals, being cold and wet can be as life-threatening as dealing with predators," Swierk said.

The spider hid under the water for about 30 minutes. As it sinks, it maintains a "film" of air surrounding its body. Swierk and colleagues suspect that the hairs covering the spider's body help it maintain an air membrane, prevent heat loss while underwater, or prevent water from entering its respiratory organs.

The air membrane surrounding the underwater spider appears to be fixed by the waterproof fur that covers its body. The spider looks like it's dipped in silver. The air membrane can act as a barrier between the water and the respiratory tract, while minimizing heat loss under the cold water stream.

According to Swierk, the observations provide new insights into how spiders deal with the problem of finding refuge in the water. "Like any animal that must hide from predators, Trechalea spiders must do their best to deal with risks, including the risk of being eaten and the risk of running away. For some species, that's the case. That means leaving a territory or a mate, or having to use up stored energy. In Trechalea spiders, the potential risks of hiding in the water can include difficulty breathing and loss of body temperature," Swierk said.

The team describes the observation in the journal Ethology on April 22. Swierk et al. suggest that there are still many questions to be answered from this first observation.